New Hot Water tank Leak or Condensation? AO Smith GCV 50 300 ProMax

I had an AO Smith GCV 50 300 ProMax 50 gal gas water heater installed last weekend. There appears to be a minor leak under the bottom lip on the back side of the tank opposite the burner. Plumber returned mid week and explained it was condensation between the inner tank and the insulation and would disappear over the next several weeks. The leak appears to be less now, maybe 1 oz or less per day. Is this normal?

Thanks Hackney,
When you say condensate are you referring to the Flue condensate from the burner gas or condensation on the exterior of the inner water tank?
Is this going to rust out my tank prematurely?

The more you drain the WH, the more the cold water in the tank can cause condensation. Also, when the burner first turns on when the tank is cold, the moisture produced when the gas is burned can condense. Once things get hot enough, it stays as vapor all the way out the flue. If the flue isn't adequate, you might be getting some spillover, too. One good test is with a smoking candle or cigarrette - see if the smoke is sucked up the flue while the burner is on. If it is lazy or backdrafts, you need to address that.

Condensation occurs when moist air contacts a cool surface, which is below the dew point for the amount of moisture in the air. The only place condensation should occur in a water heater is in the flue when the heater is initially filled with cold water. The combustion gases will condense water which will drip on to the burner causing a "sizzling" sound. After that, the water entering the heater will be partially heated on its way to the bottom of the heater, so it should never cause condensation. Besides that, the insulation around the tank will keep any moist air away from the tank. One property of a small leak in a metal tank is that it can "rust over" and stop, at least until the rust spot gets larger. I have removed the insulation from many tanks which failed because of leakage, and some looked like they were shot with a machine gun because there are so many "old" rust spots on them.

Sounds odd to me. I wouldn't expect any tank surface condensate to last for long once the tank reached temp. The only way I could see actual surface condensate posing such a problem is in a humid room with the tank being rather cold to start and sitting like that for a day or two before any heating was done. (HJ's already well covered the flue gas condensate of a cold tank.)

Here's the problem: "condensate" in the insulation requires air movement to form, you need relatively humid air to come in contact with a surface at or below the dew point. But there isn't all that much water in any given volume of air that can condense, so it would take a lot of air flow in this very restricted space for that much condensate to form in the insulation. After the tank heats up the inside wall temp is WAY past the saturated air temp, so the water will begin vaporizing easily with any air movement. So if it were really "condensation" on the tank walls it would tend to remedy itself as quickly as it occurred.

Perhaps the installer leaked a lot of water into the insulation during the install... With little air flow in the insulation, it could take a while to dry out. Of course, some thread leaks or pin hole leaks in otherwise "good" vessels will seal themselves off as well, but are likely to bite you later.

However, I wouldn't put any faith in this being just condensate or installation water until I had carefully checked all fittings/projections off the tank to make sure none were leaking water. There are a number of threaded connections on tanks, and threaded connections are common sources of leaks.

Of course there could be a pinhole leak leak in a seam weld, etc. Since it is insulated and jacketed the only way to know is by deduction. If it keeps dripping from the insulation and you can't find a leak in any projections/connections, then an actual hole in the tank is likely and you will want a warranty replacement.

I'm assuming based on your description that this isn't a simple T&P valve drip (typically caused by the lack of a thermal expansion tank.)

Condensation occurs when moist air contacts a cool surface, which is below the dew point for the amount of moisture in the air. The only place condensation should occur in a water heater is in the flue when the heater is initially filled with cold water. The combustion gases will condense water which will drip on to the burner causing a "sizzling" sound. After that, the water entering the heater will be partially heated on its way to the bottom of the heater, so it should never cause condensation. Besides that, the insulation around the tank will keep any moist air away from the tank. One property of a small leak in a metal tank is that it can "rust over" and stop, at least until the rust spot gets larger. I have removed the insulation from many tanks which failed because of leakage, and some looked like they were shot with a machine gun because there are so many "old" rust spots on them.

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You really need to read up on condensation in reference to a water heater.

" water entering the heater will be partially heated on its way to the bottom of the heater, so it should never cause condensation."

Have you EVER returned a leaking water heater to the manufacturer? The only thing I ever send to him is the rating plate with the serial number. The heater goes into the scrap heap. NO ONE looks at it or tests it. They do not explain HOW the damp air gets in contact with the heater's exterior when the insulation is bonded to it. It looks like a bunch of "engineer speak", with little relevence to the real world.

Have you EVER returned a leaking water heater to the manufacturer? The only thing I ever send to him is the rating plate with the serial number. The heater goes into the scrap heap. NO ONE looks at it or tests it. They do not explain HOW the damp air gets in contact with the heater's exterior when the insulation is bonded to it. It looks like a bunch of "engineer speak", with little relevence to the real world.

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Not to the manufacturer but I have to the dealer. Most of the time they only want the sticker off the old one but I can tell you for a fact Rheem has picked up old heaters from my dealer. Usually its when they get a run of leakers and want to determine why.

HJ in a humid climate condensation problems are compounded. While I agree the foam insulation has helped in very humid climates they can still sweat. Remember you live in a fairly dry climate......here you can almost drink the air on alot of days.

OK...everyone calm down. We all know that there can be condensation on the BOTTOM of a gas tank, especially on first start up when the tank is "ice cold" so to speak. In winter, if someone flat runs the tank out of hot...filling a bath or something, the incoming water is not going to get warmed up much as it goes towards the bottom

NOW....the OP here described a drip in an area that I would not immediately suspect as condensation, so I don't know if we have answered his question. I hope if the issue persists, he gets another plumber to look at it.

I still don't know what is causing the small leak. I did try the smoke test and the flue draws well, no visible condensation in the hood on top of the heater. I will wait another week or 2 to see if the leak dissapears and if not will call the plumber who installed it back. Thanks to all who expressed their opinions.

Adding to the condensing flue gas, it will happen in the flue within the tank as well when the tank is fully cold. I've directly observed the drops. It is more obvious on the top of the chamber itself, but the flue pipe will also produce droplets at least in the lower sections. (It's a fairly standard partial condenser configuration where the gas velocity is not so high as to entrain the liquid drops out the top.) Until the flue wall temp exceeds the saturation temp of the flue gas this condensation will occur.

Adding to the condensing flue gas, it will happen in the flue within the tank as well when the tank is fully cold. I've directly observed the drops. It is more obvious on the top of the chamber itself, but the flue pipe will also produce droplets at least in the lower sections. (It's a fairly standard partial condenser configuration where the gas velocity is not so high as to entrain the liquid drops out the top.) Until the flue wall temp exceeds the saturation temp of the flue gas this condensation will occur.

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The tank has been in and hot for over 10 days now and is still leaking. I think the plumber is hoping any holes or weld defects in the inner tank lime over and seal the leaks. I have no confidence in that approach.

I don't believe "condensate" is a proper verb. It is a noun. In this case "condensate" is being used as a verb to describe the condensation occurring on the outer tank surface. It's a new usage form that seems to be creeping up as a way of describing the situation in fewer words, but since it is already a noun it doesn't sound right. One could use the verb dew or sweat/perspire or refer to it as dewing or sweating but these verbs often imply specific mechanisms: sweating carries the connotation of liquid emerging onto a surface from within, and dewing is associated with cooling from radiant heat loss. There is probably a better verb to replace this use of condensate, but I can't think of it at the moment.

Had an intern engineer once who kept putting a superfluous "tate" at the ends of many verbs, particularly "orient." He was a sharp guy though...a bit quirky, but bright.

Exactly...I used it to describe condensation without using alot of words. Frankly it doesn't make two F'ks to me or anyone else........its just this guys way to not add anything useful to the thread but still make a post.

I had an AO Smith GCV 50 300 ProMax 50 gal gas water heater installed last weekend. There appears to be a minor leak under the bottom lip on the back side of the tank opposite the burner. Plumber returned mid week and explained it was condensation between the inner tank and the insulation and would disappear over the next several weeks. The leak appears to be less now, maybe 1 oz or less per day. Is this normal?

Thanks in advance for your advice.

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Update:

We left home for a week, before leaving we shut off water to tank, shut off burner and gas. When we returned today, no water under the tank.
Fired up the heater and now we will see if it any water leaks. The water heater is in the same small room as the furnace and was a constant 66 degrees.
If the initial problem was condensation we shouldn't see any more leaking as the 50 gals in the tank was at room temp when fired up today.

Tank is leaking again. It appears having water pressure and hot water in the tank resulted in the leak starting again.

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Sounds like the tank has a pinhole leak. It needs to go back under warranty. Plumber needs some pressure from you to to take care of the issue. Others will correct me if I am mistaken, but the plumber probably doesn't get a dime from the manufacturer for tearing out the defective tank and replacing it, so to him having to do so is lost time & money. (Car dealerships are different...they like warranty work as they get paid directly from manufacturer for labor...in slack times they get all happy when you find some obscure recall that applies to your VIN#.)

Stuff like this happens. (I even got a defective/deformed toilet tank from Toto that I took back to the supply house for another...this sort of defect in a Toto is apparently extremely rare.)